Experimental visualization of the gas-liquid two-phase flow inside the multi-cavity of a real-size marine piston model

Abstract

In the last decade, the marine industry has been pursuing higher combustion pressure and higher fuel economy, which makes the thermal load on the piston will increase significantly. Therefore, the efficient cooling of the piston is a crucial factor for reliable operation of the diesel engine. There are different types of cooling cavities inside the piston, which is usually cooled by "cocktail shaker" cooling mechanism. In the previous studies, simplified models were mostly used instead of complex actual models, and very few experiments were studied to investigate the multi-cavity with long-strokes, making it a challenge to analyze the gas-liquid two-phase flow in the complex piston cooling cavity. In this paper, a visualization test rig of a real-size marine piston model was built to observe the complex multi-cavity flow by using high-speed camera equipment. Flow mechanism of two-phase flow inside the multi-cavity piston is revealed, the variation of flow patterns with the rotational speed and the filling rate is also studied. It is found that swirl flow exists inside the multi-cavity piston, which was mostly neglected in previous studies. Experimental observations are also verified by extended simulation investigation of the flow field. Results of this paper reveal the full flow mechanism of a typical marine multi-chamber piston, and provide foundation and reference to the cooling mechanism study and optimal design of piston cooling system.